Cumulative sum by month with missing months - sql

Question

I have to cumulative sum by month a quantity but in some months there's no quantity and SQL does not show these rows.
I have tried multiple other solutions I found here but none of them worked or at least I couldn't get them working. Currently, my code is as follows:
SELECT DISTINCT
A.FromDate
,A.ToDate
,A.OperationType
,A.[ItemCode]
,SUM(A.[Quantity]) OVER (PARTITION BY [ItemCode],OperationType,YEAR ORDER BY MONTH) [Quantity]
FROM (
SELECT
CONVERT(DATE,DATEADD(yy, DATEDIFF(yy, 0, T.OrderDate), 0)) AS FromDate
,EOMONTH(T.OrderDate) ToDate
,DATEPART(MONTH, t.OrderDate) AS [Month]
,DATEPART(YEAR, t.OrderDate) AS [Year]
,SUM(T.[Quantity]) [Quantity]
,OperationType
,[ItemCode]
FROM TEST T
WHERE [ItemCode] != ''
GROUP BY T.OrderDate,[ItemCode],OperationType
) A
With these results:
FromDate
ToDate
OType
ItemCode
Quantity
2021-01-01
2021-01-31
Type1
1
19
2021-01-01
2021-02-28
Type1
1
96
2021-01-01
2021-03-31
Type1
1
116
2021-01-01
2021-04-30
Type1
1
138
2021-01-01
2021-06-30
Type1
1
178
2021-01-01
2021-07-31
Type1
1
203
2021-01-01
2021-08-31
Type1
1
228
2021-01-01
2021-09-30
Type1
1
253
2021-01-01
2021-11-30
Type1
1
330
2021-01-01
2021-12-31
Type1
1
364
2022-01-01
2022-02-28
Type1
1
18
2022-01-01
2022-03-31
Type1
1
42
2022-01-01
2022-04-30
Type1
1
53
And I was expecting these results:
FromDate
ToDate
OType
ItemCode
Quantity
2021-01-01
2021-01-31
Type1
1
19
2021-01-01
2021-02-28
Type1
1
96
2021-01-01
2021-03-31
Type1
1
116
2021-01-01
2021-04-30
Type1
1
138
2021-01-01
2021-05-31
Type1
1
138
2021-01-01
2021-06-30
Type1
1
178
2021-01-01
2021-07-31
Type1
1
203
2021-01-01
2021-08-31
Type1
1
228
2021-01-01
2021-09-30
Type1
1
253
2021-01-01
2021-10-31
Type1
1
253
2021-01-01
2021-11-30
Type1
1
330
2021-01-01
2021-12-31
Type1
1
364
2022-01-01
2022-02-28
Type1
1
18
2022-01-01
2022-03-31
Type1
1
42
2022-01-01
2022-04-30
Type1
1
53
SQL Fiddle link: http://www.sqlfiddle.com/#!18/04a997/1
I would really appreciate some help. Thank you

Answer 1

Here is one way:
WITH m(Earliest,Latest) AS
(
SELECT DATEADD(DAY,1,MIN(EOMONTH(OrderDate,-1))),
MAX(EOMONTH(OrderDate)) FROM dbo.TEST
), TypeCodes AS
(
SELECT DISTINCT ItemCode, OperationType
FROM dbo.TEST
), Months AS
(
SELECT Month = DATEADD(MONTH, ROW_NUMBER()
OVER (ORDER BY ##SPID)-1, Earliest)
FROM m CROSS APPLY STRING_SPLIT(REPLICATE(',',
DATEDIFF(MONTH,Earliest,Latest)),',')
), raw AS
(
SELECT m.Month, i.OperationType, i.ItemCode,
Q = COALESCE(SUM(Quantity),0)
FROM Months AS m
CROSS JOIN TypeCodes AS i
LEFT OUTER JOIN dbo.TEST AS t
ON t.OrderDate >= m.Month
AND t.OrderDate < DATEADD(MONTH, 1, m.Month)
AND i.ItemCode = t.ItemCode
AND i.OperationType = t.OperationType
GROUP BY m.Month, i.OperationType, i.ItemCode
)
SELECT FromDate = Month,
ToDate = EOMONTH(Month),
OperationType,
ItemCode,
Quantity = SUM(Q) OVER (ORDER BY Month)
FROM raw;
Working example in this fiddle.
If you can't use STRING_SPLIT() because your database is stuck on an older compatibility level, you could put this function in a database that isn't:
USE ModernDatabase;
GO
CREATE FUNCTION dbo.StringSplit(#list nvarchar(max), #delim nchar(1))
RETURNS TABLE
AS
RETURN (SELECT value FROM STRING_SPLIT(#list, #delim));
Then you change:
FROM m CROSS APPLY STRING_SPLIT(...
To:
FROM m CROSS APPLY ModernDatabase.dbo.StringSplit(...